1. Field of the Invention
The present invention relates to an ink set suitable for forming an image and a method for forming an image.
2. Description of the Related Art
Recently, an aqueous colored dispersion in which an insoluble solid such as a pigment is dispersed in water has been actively used for applications such as ink for inkjet recording.
In recent years, a variety of methods have been suggested as image recording methods for recording a color image. In such a method, there is an increasing demand for high quality of recorded materials such as fineness of images, texture, and resistance to water or abrasion or the like.
For example, an inkjet technology is widely applied to the fields such as office and home printers and furthermore has recently been applied to commercial printing fields. For this reason, the demand for quality in recorded materials is having a tendency to further increase. In particular, for stability of images required for recorded materials, more specifically, abrasion resistance or ink ejection stability necessary for image formation, performance improvement is further required.
In this regard, an ink set combining a recording liquid containing a pigment coated with a resin and a treatment liquid containing a cationic compound having reactivity to the resin-coated pigment is disclosed (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2003-266916) and it is believed that printed materials with superior abrasion resistance can be obtained therefrom.
In addition, a method for forming an image wherein an inkjet recording ink using a polymer emulsion in which a pigment is contained in a polymer such as vinyl-based polymer including styrene as a structural unit is ejected to a recording material to which a pretreatment liquid containing a water-soluble organic acid has been applied to form an image is disclosed (for example, see JP-A No. 2009-166387).
However, the conventional ink uses a substance having a styrene-based structural unit as a hydrophobic component of resin components for coating a pigment and abrasion resistance effects thereof to some extent are expected. Recently, required image quality, in particular, abrasion resistance, when external force is applied, has not necessarily been sufficient.
In addition, when the content ratio of resin component in the ink increases in order to improve abrasion resistance, the problem, for example that the ink may be readily adhere to an ejection head is caused by the reasons such as the difficulty of redissolving the adhered ink in the ink. As a result, the ejection of ink cannot be stably maintained and furthermore, the landing position precision of ink is disadvantageously deteriorated.